I've got over 2,000 miles on my rebuild, and when it warms up, I get a smell of coolant for a minute or two. Also, there seems to be excessive blowby at some point, but it is not noticeable after warmup. (PCV ok.)

Second bit of info: It would appear that the heads/block were surfaced more than the machinist remembered. There is a very obvious difference between the intake manifold and the head, where they join at the valve cover surface. It is about a 1/16" difference.

I wonder if there is a mismatch at the intake manifold, causing a minor leak of oil and coolant, which then stops as soon as the engine gets hot.

Other clues: oil leak behind the engine somewhere, no coolant leak tracer marks and only a tiny amount is lost, plugs are not much help, as it just gained 6,000 feet in elevation, and they went from white to dark brown as expected, no extended steam from tailpipe, using a .020 steel shim head gasket with copper spray-on sealant, using old original head bolts....

OK, any ideas?

 

Do a compression check, when cold, it'll tell you if you have any obvious issues.

That coolant smell is a tricky one - could be the heater core, or the radiator weeping.

If the intake and the heads are that much mismatched, the holes wouldn't line up very easily, would they? Aftermarket or stock intake?

 

When I installed my intake the first time it matched up perfectly, when I did it again I got a mismatch. So what you have might not be due to machine work.
puttster

 

Stock everything, and they should be the original stock heads.

Ok on the cold compression test. Good thought.

 

Have you checked the sending units for tightness?

 

How many sending unit(s) are there for water, and where are they Cliff?

 

Sending units... Yes, and all are snug, with teflon tape. By the time the engine is hot enough, I'm going down the road, so catching it in action has been tough. I haven't been able to find a green-streak anywhere. There is some greasy green residue topside, but no obvious spot where it leaks. The quantity is fairly small.

Still haven't found the source of a potential vacuum leak - might be a missing gasket in the choke housing leg, but it doesn't speed up with application of carburetor or ether starting spray.

Putster: That is an interesting observation.
When I did my torque-down of the heads and intake manifold, I did the triple-method. I don't have it handy, but both heads and the manifold are tightened down in many stages, getting tighter in smaller steps all the way down to the final values. I sure hope that works on FEs like it does on other V8 engines! There are locating dowels to keep the heads on straight.

I'm pretty sure using the original steel-shim head gasket is not the way to go for a decked block and shaved head. I could kick the machinist for not keeping track of the exact amounts taken off... I wonder if he goofed, and shaved them to cover it up. I needed .040 pedestal shims to correct for the 'shave'. I did say that I'd be happy with a higher CR, since my engine was an 8.2 version.

 

Oil leak behind the engine is more than likely from the valve cover gasket due to the mismatch. They can be a bitch getting them to seal under good conditions.